Performing maintenance work on a gas pipeline can often cause an undesirable disruption of service for gas customers. Although some work may be performed while the pipeline is “live”—i.e., the gas is still flowing through the pipeline—other types of work may require a stoppage of gas flow at least through the localized work area. In some cases, because of redundancies in networks, gas may still reach most or all of the gas customers despite the localized stoppage. In cases where there are not sufficient redundancies, however, gas service to a large number of customers may be cut off completely while work on the pipeline is performed. This may be a particular problem where a relatively large opening is required to access the pipeline, and also in cases where a physical connection is required between the outside of the pipeline and the inside of the pipeline while the work is being performed.
One such situation may occur when a pipeline apparatus such as a relatively large robotic device needs to be inserted into the pipeline to perform inspection or repair. Further complicating matters is the situation where a physical connection is required between the robotic device inside the pipeline and another system or device outside the pipeline—e.g., for purposes of communications, power transfer, etc. Although a live gas main can be tapped and have a valve installed over the opening, it may still be difficult to access the pipeline to perform maintenance if the gas is not cut off. It may be desirable, therefore, to have a secondary structure attachable to the pipeline that provides ingress and egress to and from the live gas main.